<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        for(;;){
        let  uname=  prompt('输入用户名')
        let  psw= prompt('输入密码')
            if (uname==='admin' && psw==='123456') {
                alert('登录成功')
                break 
            }        
        }
    </script>
</body>
</html>